1. Field of the Invention
The present invention relates to a forming board sheet for use in heat forming processes for molding automobile rear window ledges or trays, automobile dome liners, or other parts for automobile interior, and other types of structural materials, various types of packaging materials, etc. More particularly, it relates to a low-moisture content layered sheet, at least one layer of which comprises cellulose fibers, a polyolefin, and an inorganic filler.
2. Prior Art
Hardboard is used extensively both domestically and industrially due to its low cost and ease of manufacture. Hardboard usually comprises a cellulose fiber such as ground wood, water, and a binder such as latex, starch or urea formaldehyde. Of hardboards having the aforementioned compositions, those in which the binder is latex or non-cured urea formaldehyde are known as formable hardboards in that a hardboard sheet of this composition can be formed in a hot press with the application of heat and pressure.
As presently as practiced, the method of heat forming hardboard includes the steps of placing a sheet of hardboard which has been soaked in water and allowed to age in the wet state for several days and then steamed or dipped in hot water before use between upper and lower platens of a die, bringing the platens together while applying heat and pressure to the hardboard whereby the hardboard is softened and formed in the die, separating the platens, and removing the hardboard form from the die. During this forming operation, the heat and pressure cause the hardboard to generate gases and vapours which are entrapped within the hardboard by the die causing blisters and defects in the finished formed hardboard.
Accordingly, it would be desirable to have a low-moisture content forming board to replace the hardboards of the past, so as to reduce the tendency to generate such gases and vapours during the heat forming operation. More significantly, it would be desirable to eliminate the need for soaking and steaming or dipping the board before use. These steps require the expenditure of time and money. In addition, they necessitate the use of cumbersome, energy consuming equipment.